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13 HDD sysetm needs PSU

L

lordsegan

Gawd
Joined
Jun 16, 2004
Messages
624
I am building a system with 13 HDDs. What size/type of PSU do I want for reliable multi year operation?
 
13 HDD's on there own don't consume all that much power, 150w at the absolute high end. Roughly double that during startup for a few seconds. Depending on the rest of the system specs, you could easily get by with a 400+ watt PSU. If these are low RPM storage drives, then power consumption will be significantly less then my above estimates...which are already really high, even for 7200rpm drives.

Bottom line is almost any modern power supply could handle that many drives. So don't stress about it too much. You'll of course need to add a few connectors here and there, as its rare to find a PSU with 13 sata power connectors.
 
CX430 V2 when it goes on sale for $20, if you're in no hurry.
 
Any quality 350w PSU can handle that rig...so just buy what's on sale. The low power Seasonic units are really nice as they are incredibly quiet.
 
My experiments with 18 drives (6 7k1000, 6 7k2000, and 6 5k3000s) show the following. I measured wall draw with a Kill-A-Watt meter, and all the drives were fully spun up and idle.
Zero disks: 146W
6*5k3000: 176W
6*7k2000: 178W
7k2+5k3: 217W
All 18: 255W

So the 6 5k3s draw 30W total, the 7k2s draw 32W, and when you combine them, those 12 disks draw 71W. I'm guessing this is just inaccuracy in my measurement. Finally, all 18 disks draw 109W, or about 6.1W each.

Booting the system (which causes continuous low-level activity) raises the total to 265W. Assuming that this additional load is entirely disk-based means that each disk is now drawing about 6.7W. Assume it takes twice that to spin each disk up nicely; then you need 6.7*13*2W to spin up the drives, plus 150W to run the rest of the system. This is a total of 324W.

Accounting for aging capacitors in the power supply is worthwhile, so I might buy a 600W unit to get a couple years out of the machine. For my personal fileserver, I bought a 1050W power supply so I can keep it happy for a long time.
 
Aging in capacitors is an overhyped myth, you do not need to account for that at all.
 
What size drives are you using if you don't mind me asking? Just curious how much drive space you'll have. :D
 
unhappy_mage said:
I hadn't heard of this before. Here are some things I dug up researching the subject.
A discussion on the subject from a European capacitor manufacturer
Emerson, who makes large UPS units, discusses the topic.

Do you have any articles on this phenomenon? I've definitely noticed older power supplies becoming unstable under loads they used to handle.
Click to expand...

It's not that it doesn't happen. It's just that the components used in quality power supplies for the past 3-5 years are much better than ones used before then. By the time the capacitors start to show any noticeable decrease in quality, usually something else in the PSU has already failed.
 
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